Method of making aluminum bronze articles



Aug. 27, 1968 Filed Oct. 11, 1965 PS]. x/000 E LONG/1 77 ON "/0 G. H. EICHELMAN, JR, ET AL 3,399,084

METHOD OF MAKING ALUMINUM BRONZE ARTICLES 3 Sheets-Sheet 1 com ROLLED 20% TENS/LE STRENGTH YIELD STRENGTH (40.2 /0 OFFSET) YIELD STRENGTH (0.1% OFFSET) DEGREES FAHRENHE/ 7' [l6 J INVENTORS.

GEORGE H. E/CHEL MAN JR.

mwuv B/POl/ERMAN ATTORNEY Aug. 27, 1968 G. H. EICHELMAN, JR., ET AL METHOD OF MAKING ALUMINUM BRONZE ARTICLES Filed Oct. 11, 1965 R51 X /OOO E LONGA 770M /0 COLD ROLLED 40% 5 Sheets-Sheet 2 U0 TENS/LE STRENGTH WELD STRENGTH (0.2 OFFSE T/ V/ELD STRENGTH (0.1% orrsa T/ /25 /00 FIG-2 DEGREES FA HRENHE/ T INVENTORS. GEORGE H. E/CHELMANJ/e IRWIN BROl ERMAN Z 1L (34: WA

. A TTOR/VEV G. H. EICHELMAN, JR, ET AL 3,399,084

METHOD OF MAKING ALUMINUM BRONZE ARTICLES Aug. 27, 1968 3 Sheets-Sheet 3 Filed Oct. 11, 1965 cow ROLLED 60 "/0 TENS/LE STRENG 7H WELD STRENGTH (0.2 /0 OFFSET) YIELD STRENGTH (0.1 /0 oFFsErj 5 0 w w v m w m QQQ m Q \0 EOE VGEQQM DEGREES FAHRENHE/T FIG 3 A TTORNEY 3,399,084 METHOD OF MAKING ALUMINUM BRONZE ARTHCLES George H. Eichelman, .lr., Cheshire, Conn., and Irwin Broverman, Chicago, 11]., assignors to Olin Mathieson Chemical Corporation, a corporation of Virginia Filed Oct. 11, 1965, Ser. No. 494,596 14 Claims. (Cl. 148-115) The present invention relates to improved aluminumbronze alloys and to the preparation thereof. More particularly, the present invention resides in novel and inexpensively prepared high strength copper base alloys containing from 9.0 to 11.8% aluminum and the balance essentially copper.

In co-pending application Ser. No. 328,184, filed Dec. 5, 1963, and now Patent No. 3,287,180, by George H. Eichelman, Jr., and Irwin Broverman, there is described novel aluminum-bronze alloys and the method of fabricating same, said alloys containing from 9.0 to 11.8% aluminum and the balance essentially copper. These improved alloys have a metallographic structure containing from 5 to 95% beta phase and the remainder alpha phase. In addition, these alloys have a uniformly fine metallographic grain structure with a grain size less than 0.065 mm. These alloys readily obtain a combination of strength and ductility heretofore unobtainable in alloys of this type. For example, tensile strengths ranging from 110,000 to 120,000 psi. and yield strengths from 44,000 to 52,- 000 (0.2% offset) were developed in combination with elongations ranging from 9 to 12%.

In co-pending application Ser. No. 341,121, filed Jan. 29, 1964, and now Patent No. 3,297,497, by George H. Eichelman, Jr., and Irwin Broverman, there is described a mechanism for obtaining still greater improvement in alloys of this type. This improvement is obtained by the addition of from 0.05 to 5.0% of at least one additional element having a solid solubility in copper of less than 4.0% and which forms at least one intermetallic compound with aluminum. The total quantity of said additional elements is less than 10.0 percent. For example, iron, chromium, titanium, zirconium, molybdenum, c0- lumbium, vanadium and mixtures thereof. The overall effect of co-pending application Ser. No. 341,121 is to develop even higher strength levels for comparable ductilities. For example, Ser. No. 341,121 attains tensile strengths ranging from 120,000 to 160,000 psi. and yield strengths ranging from 60,000 to 80,000 psi. (0.2% offset) in combination with elongations ranging from 12 to 9% In accordance with the present invention, it has now been surprisingly found that with a different mechanism we obtain comparable physical properties and frequently greater strength levels, particularly yield strength. This is particularly surprising in view of the simple and expeditious nature of the process of the present invention.

The process of the present invention is a method for fabricating a high strength aluminum-bronze alloy containing from 9.0 to 11.8% aluminum and the balance essentially copper which comprises: hot working an alloy having the aforesaid composition at a temperature of from 1850 to 1000 F.; cold working said alloy at a temperature below 300 F.; and holding said alloy for at least 15 minutes at a temperature of from 350 to 650 F.

A particular advantage of the alloys and process of the present invention is that the alloy could be supplied as cold rolled. The customer could put the cold rolled material in a conventional, low temperature oven and obtain the improvements of the present invention for use as a formed part and so forth.

The present invention is applicable to copper base alloys containing from 9 to 11.8% aluminum. The aluminum content must critically be within the aforementioned States Patent 0 See range, preferably is within the more limited range 9.4 to 10.4% aluminum, and optimally is between 9.4 and 10.0% aluminum.

The alloys of the present invention preferably contain from 0.05 to 5.0% of at least one additional element which has a solid solubility in copper of less than 4.0% and which forms one or more intermetallic compounds with aluminum, with the total quantity of said additional elements being less than 10.0%. The additional element is preferably selected from the group consisting of the following preferred amounts: iron from 2.0 to 5.0%; chromium from 0.4 to 2.0%; titanium from 0.4 to 2.0%; zirconium from 0.05 to 0.2%; molybdenum from 0.4 to 2.0%; columbium from 0.4 to 2.0%; vanadium from 0.4 to 2.0%; and mixtures thereof. The preferred additional elements are iron, chromium and zirconium.

The additional element should be an intermetallic compound former with aluminum and should in fact preferentially form intermetallic compounds with aluminum. In addition, the additional element and/ or intermetallic compounds formed should preferably form a dispersion in copper with limited solid solubility at temperatures up to 1800 F.

The remainder or balance of the alloy is essentially copper, i.e., the alloy may contain incidental impurities or other materials which do not materially degrade the physical characteristics of the alloy. Exemplificative materials include tin, zinc, lead, nickel, silicon, silver, phosphorus, magnesium, antimony, bismuth and arsenic.

The improved alloy of the present invention is obtained in accordance with the critical series of steps outlined above.

The first critical step in the process of the present invention is the hot working step in the aforementioned critical temperature range. Preparatory to the hot work ing step the alloy may naturally be melted and cast in a suitable bar or ingot form using conventional practices to insure compositional and structural homogeneity. For example, cathode copper may be induction melted under a charcoal cover or suitable salt flux. High purity or commercial aluminum in the requisite quantity may then be added and the melt thoroughly stirred to insure adequate mixing. The additional elements may be added in the same manner, that is, high purity or commercial iron, chromium, titanium, zirconium, molybdenum, columbium, and/or vanadium may be added in the desired amount and the melt thoroughly stirred to insure adequate mixing. The molten charge may then be cast by any commercial method which will insure a sound cast structure that is essentially free from entrained aluminum oxide.

The foregoing is, of course, intended to be illustrative and not restrictive. It is only necessary that there be provided a homogeneous, sound and clean aluminum-bronze alloy satisfying the foregoing compositional requirements.

As stated above, the alloy is hot worked in the foregoing temperature range. The term hot working is employed in its conventional sense. In accordance with the present invention, however, hot rolling is the preferred operation and the present process will be described in more detail with reference to this preferred mode of operation.Naturally, other methods of hot working will readily suggest themselves to those skilled in the art, e.g., forging and extrusion.

The manner of bringing the material into the hot holling temperature range is not critical and any convenient heating rate or method may be employed.

The temperature of hot rolling is, as stated above, from 1850 to 1000 F., with it being preferred to utilize a narrower temperature range of from 1650 F. to 1000 F.

In the process of the present invention, the as-cast material may simply be heated up to the starting temperature. The time at temperature is not critical and generally the casting is simply held long enough to insure uniformity of temperature. We then may hot roll directly from this temperature. During rolling of the ingot, some cooling occurs through natural causes. It is not necessary to maintain the ingot at any one starting temperature. In fact, it is preferred not to maintain the ingot at any one starting temperature, since, as the material cools alpha phase continuously precipitates and the series of reductions at progressively lower temperatures results progressively in structural refinements. In other Words, it is preferred to commence the hot rolling at the more elevated temperatures in the hot rolling temperature range and gradually decrease the temperature in order to refine the .grain structure.

The length of time of hot rolling is not critical. The alloy may, if desired, be hot rolled until reaching the lower temperature in the hot rolling temperature range, i.e., 1000 F.

Subsequent to the hot rolling step, the alloy contains the maximum amount of alpha phase possible, as governed by the phase equilibrium for the particular composition. If an additional element is included as above, the alloy also contains a relatively large volume of the previously described dispersion. In the preferred embodiment, the maximum amount of alpha phase is obtained by insuring that the alloy either during or subsequent to hot rolling is held in the temperature range of 1050 to 1100 F. for at least two minutes. This may be done in a variety of ways either during the hot rolling or by a thermal treatment subsequent thereto. For example, the alloy may be cooled slowly through this temperature range during the normal course of hot rolling and held there for at least two minutes and preferably longer. Alternatively, this holding step may be combined with an optional intermediate anneal. The optional intermediate anneal should be at 1050-1400 F. for at least 15 minutes.

Subsequent to the hot working step the alloy is cold worked at a temperature of below 300 F., and preferably from to 200 F. The term cold working is employed in its conventional sense. In accordance with the present invention, however, cold rolling is preferred and the present process will be described in more detail with reference to this preferred mode of operation. Naturally, other methods of cold working will readily suggest themselves to those skilled in the art, for example, drawing, swaging, and cold forging.

The reduction effected during the cold rolling step is dependant upon many factors. If no additional rolling steps are to be performed, the alloy may be cold rolled to final gage. The exact percentage reduction in the cold rolling is not critical, with the percentage and number of cold rolling steps dependant upon manufacturing economics. If desired, in order to minimize the cold rolling reduction, the alloy may be reheated within the specified hot rolling range and the further reduced to a smaller thickness for cold rolling. In general, however, the greater the cold rolling reduction in the final cold roll, the higher the physical properties that will be developed upon subsequent treatment in accordance with the present invention.

After the cold rolling step the alloy is in the temper rolled form.

After the cold rolling reduction has been taken, the low temperature holding step or low temperature thermal treatment step of the invention is performed. In accordance with this step, the alloy is held for at least minutes at a temperature of from 350 to 650 F., preferably from 400 to 550 F. The maximum holding time is not especially critical, but no particular advantage is seen in holding periods in excess of 16 hours.

If desired, and in fact in the preferred embodiment, subsequent to the cold rolling step but before the low temperature holding step of the present invention, there is performed an annealing step which in turn is followed by an additional cold rolling step. The cycle of annealing and cold rolling may be repeated as often as desired to retain the necessary reduction. In fact, in the preferred embodiment, two such cycles are performed.

The annealing temperature is from 1000 to 1400 F., preferably from 1000 to 1100" F. and optimally from 1050 to 1100 F. For some of the alloys of the present invention the preferred annealing temperature may be higher in order to achieve a particular purpose, for example, the iron-containing alloy may be annealed at from 1300l400 F. following which best cold rollability has been observed. The alloy should be held at this elevated temperature for at least two minutes.

It should be noted that in accordance with the process outlined in the above co-pending applications high strength characteristics were obtained by heat treating the alloy after cold rolling at a critical elevated temperature range followed by rapid cooling. This heat treatment converted most of the alloy to the beta phase. In the rapid cooling the alloy retained a high proportion of beta phase and the beta phase underwent a structural transformation known as a martensitic transformation which resulted in a significant strength increase. The combination of heat treatment and rapid cooling was termed a betatizing procedure.

On the other hand, the process of the present invention does not employ a betatizing step but attains surprisingly high strength levels without this procedure. In fact, in accordance with the present invention it is essential to utilize a high proportion of alpha phase. In fact, after the treatments of the present invention, the resultant alloy of the present invention contains from 50 to 100% alpha phase and preferably from to alpha phase. It is particularly surprising that this is the case, especially in view of the findings of the above co-pending applications.

As a result of the process of the present invention the yield strength generally increases by at least about 20% while the ultimate strength generally increases to a smaller degree. This anomalous increase in strength of the alloys of the present invention may be attributed to dislocation tangles in the sub-microstructure of the alloys as seen by using electron transmission microscopy. The specific hardening may be attributed to the colonizing of these diffusion tangles into a regular pattern of a cellular nature, with the cells and the diffusion tangles locked in place. Thus we can term the sub-microstructure as containing interlocked diffusion tangles.

In general, for example, the minimum tensile properties are for the 40% cold rolled material, at least about 120,000 p.s.i. and generally above 140,000 p.s.i., and for the 40% cold rolled plus low temperature thermal treated, at least about 130,000 p.s.i.

The present invention and improvements resulting therefrom will be more readily apparent from a consideration of the following illustrative examples.

Example I Alloys having the following compositions were prepared from a charge of cathode copper, aluminum-iron master alloy and commercial purity aluminum in the form of 2 /2 x 12" x 30" DC castings.

Alloy 1.-Al9.8%, l e-4.1%, Cuessentially balance.

Alloy 2.Al9.5%, Fe-4.9%, Cu-essentially balance.

Each of the alloys were hot rolled in the temperature range of from 1600 to 1300 F. Reductions of about 5 to 10 percent per pass were used in reducing the gage from 2.5" to 0.35". These reductions were limited primarily by the roll diameter with greater reductions readily obtainable.

Example II The following example is comparative in nature and shows the results obtained in accordance with co-pending application Ser. No. 341,121.

Following hot rolling to an intermediate gage of 0.35" as in Example I, a specimen of alloy 2 (Al9.5%, Fe 4.9%, balance essentially copper) was held at 1150 F. for 30 minutes and subsequently air cooled for maximum cold rollability. The alloy was cold rolled from 0.35" to 0.030" gage, reducing the thickness 40% with interannealing at 1150 F. A grain size of 0.010 mm. in diameter was developed in the alloys. The microstructures of the alloys contained a discrete, uniformly distributed dispersion rich in iron.

Prior to cold rolling but after holding at 1150 F. the alloy had the following properties:

Yield strength, p.s.i 50,000

Tensile strength, p.s.i 96,000 Elongation, percent 33 The final cold rolling of this alloy 54% gave the following properties:

Yield strength, p.s.i 115,800 Tensile strength, p.s.i 148,000 Elongation, percent 2 The above alloy was betatized to produce maximum beta phase by holding at 1628 F. for 30 minutes followed by water quenching to give:

Yield strength, p.s.i 64,000 Tensile strength, p.s.i 161,000 Elongation, percent 7 Example III This example shows the results obtained in accordance with the present invention.

Following hot rolling, alloy 1 in Example I (Al-9.8%, Fe-4.1%, balance essentially copper) was held at 1150" F. and cold rolled in a manner after Example 11 with intra-anneals at 1150 F., with final cold rolling reductions of 20%, 40% and 60% being taken.

After cold rolling all samples, i.e., the samples cold rolled 20%, 40% and 60%, were heat treated for 1 hour at temperatures ranging from 350 to 650 F.

The results are shown in FIGURES 1, 2 and 3 which form a part of the present specification. All figures show tensile strength, yield strength (both 0.2% and 0.1% offset) and percent elongation. FIGURE 1 shows the properties of the 20% cold rolled material, FIGURE 2 the 40% cold rolled material, and FIGURE 3 the 60% cold rolled material. In all figures the tensile strength, yield strength and percent elongation are plotted as the ordinate against the temperature of the heat treatment in degrees Fahrenheit as the abscissa.

From the drawings it can be seen that maximum strengthening is obtained by heat treatment at 450 F. It should be particularly noted that the process of the present invention effects a considerable and surprising improvement over the process of co-pending application Sen-No. 341,121, exemplified by Example II above. In addition, after the one hour heat treatment step the alloys of the present invention contained from 80-100% alpha pha'sel and the balance beta phase and the sub-microstructure contained interlocked diffusion tangles as described hereinabove.

Example IV In this example an alloy was prepared as in Example I to have the following composition:

(1) Al--%, balance essentially copper.

The alloy was hot rolled as in Example I followed by holding at 1150 F. for 30 minutes followed by cold rolling 30% as in Example 11. Subsequent to cold rolling the alloy was heat treated at 450 F. for one hour. The diamond pyramid hardness (DPH) was determined on the alloy as cold rolled and after heat treatment. The alloy was found to have the following properties: 231 DPH as cold rolled 30%; 251 DPH after heat treatment.

6 Example V Alloys having the following compositions were prepared and hot rolled as in Example I:

Alloy 3.Al9.7%, chromium1.25%, Cuessentially balance.

Alloy 4.Al-9.5%, zirconium-0.26%, Cuessentially balance.

The hot rolled alloys were then treated as in Example III, with final cold rolling reductions of 40% being taken. The properties are given below:

Yield In addition, after the one hour heat treatment step the alloys of the present invention contained from -100% alpha phase and the balance beta phase and the submicrostructure contained interlocked diffusion tangles as describe hereinabove.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What is claimed is:

1. The method of fabricating a high strength aluminumbronze alloy containing from 9.0 to 11.8% aluminum and the balance essentially copper, which comprises: hot working an alloy having the aforesaid composition at a temperature of from 1850 to 1000 F., cold working said alloy at a temperature of below 300 F.; and holding said alloy for at least 15 minutes at a temperature of from 350 to 650 F.

2. The method of claim 1 wherein said hot working is hot rolling and wherein said cold working is cold rolling.

3. The method of claim 2 including the following step prior to said cold rolling step: holding said alloy at a temperature of from 1100 F. to 1050 F. for at least two minutes.

4. The method of claim 2 including the following steps subsequent to said cold rolling step but prior to said holding step: annealing said alloy for at least two minutes at a temperature of from 1000 to 1400 F.; and cold rolling said alloy at a temperature of below 300 F.

5. The method of fabricating a high strength aluminumbronze alloy containing: (A) from 9.0 to 11.8% aluminum; (B) from 0.05 to 5.0% of at least one additional element having a solid solubility in copper of less than 4.0% and which forms at least one intermetallic compound with aluminum, with the total quantity of said additional elements being less than 10%; and (C) the balance essentially copper, which comprises: hot working an alloy having the aforesaid composition at a temperature of from 1850 to 1000 F., cold working said alloy at a temperature of below 300 F.; and holding said alloy for at least 15 minutes at a temperature of from 350 to 650 F.

6. The method of claim 5 wherein said hot working is hot rolling and wherein said cold working is cold rolling.

7. The method of claim 6 wherein said additional element is selected from the group consisting of: iron from 2.0 to 5.0%; chromium from 0.4 to 2.0%; titanium from 0.4 to 2.0%; zirconium from 0.05 to 0.2%; molybdenum 7 from 0.4 to 2.0%; columbium from 0.4 to 2.0%; vanadium from 0.4 to 2.0%; and mixtures thereof.

8. The method of claim 6 wherein said additional element is iron in an amount from 2.0 to 5.0%.

9. The method of claim 6 wherein saidadditional element is chromium in an amount from 0.4 to 2.0%.

10. The method of claim 6 wherein said additional element is zirconium in an amount from 0.05 to 0.2%.

11. The method of claim 6 including the following step prior to said cold rolling step: holding said alloy at a temperature of from 1100 F. to 1050 F. for at least two minutes.

12. The method of claim 6 including the following steps subsequent to said cold rolling step but prior to said holding step: annnealing said alloy for at least two minutes at a temperature of from 1000 to 1400 F.; and cold rolling said alloy at a temperature of below 300 F.

13. The method of claim 12 including two cycles of said subsequent annealing and cold rolling steps.

14. The method of fabricating a high strength alumid mum-bronze alloy containing: (A) from 9.0 to 11.8% aluminum; (B) from 0.05 to 5.0% of at least one additional element having a solid solubility in copper of less than 4.0% and which forms at least one intermetallic compound with aluminum, with the total quantity of said additional elements being less than 10%; and (C) the balance essentially copper, which comprises: hot rolling an alloy having the aforesaid composition at a temperature of from 1650 to 1000 F.; holding said alloy at a temperature of from 1100" F. to 1050 F. for at least two minutes; cold rolling said alloy at a temperature of below 200 F.; annealing said alloy for at least 2 minutes at a temperature of from 1000 to 1400 F.; cold rolling said alloy at a temperature of below 200 F.; and holding said alloy for from 15 minutes to 16 hours at a temperature of from 400 to 550 F.

References Cited UNITED STATES PATENTS 3,287,180 11/1966 Eichelman et al. 148-1l.5 3,290,182 12/1966 Eichelman et al. 148-115 3,297,497 l/ 1967 'Eichelman et al l48l 1.5

HYLAND BIZOT, Primary Examiner.

W. W. STALLARD, Assistant Examiner. 

1. THE METHOD OF FABRICATING A HIGH STRENGTH ALUMINUMBRONZE ALLOY CONTAINING FROM 9.0 TO 11.8% ALLUMINUM AND THE BALANCE ESSENTIALLY COPPER, WHICH COMPRISES: HOT WORKING AN ALLOY HAVING THE AFORESAID COMPOSITION AT A TEMPERATURE OF FROM 1850 TO 1000*F.; COLD WORKING SAID ALLOY AT A TEMPERATURE OF BELOW 300*F.; AND HOLDING SAID ALLOY FOR AT LEAST 15 MINUTES AT A TEMPERATURE OF FROM 350 TO 650*F. 